I think this is due to the bus being cut in half due to the added card. He is most likely not running a mainboard that supports 2 slot full 16X for each. This is why he is feeling a hit on performance. Had the same issue with mine.

I tried the 9800GT I was using with my GTX 295 in my upgraded system and saw no increase in performance when testing out Metro 2033. My Vantage score and performance in the games I tested even dropped slightly. The drop in my performance may have been due to the fact that my second 480 card was running at 8X PCIe speed as opposed to the full 16x like my first card. The physx card also made the temps go up some on my 480 cards.

I think, unless future drivers change this, that using a dedicated physx card in a GTX 470/480 SLI setup is a waste of time.

But even with a single GPU system I wouldn't want a second dual slot GFX cards (9800GTX or better) in my system just because I'd get a few FPS more in very few games...

Probably true for most people. My main motivation was that a friend "fried" it with those graphics drivers that were killing cards... I baked it and she turned out to be a solid card for the $30 they wanted to sell it for.

It gives me another 7,000 keys/sec compared to my 14,000 on my GTX 285 in linux while testing wpa passwords.... so for $30 that's my sole justification for it.

What you're saying is probably true, most people can't find a 2nd card powerful enough at a price that's good enough to justify it for physx alone, and probably no one else on these forums can find a use for a 2nd card outside of physx. Rather a special case with me